• Nuclear Engineering and Technology
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• 제41권5호
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• pp.739-746
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• 2009

This paper introduces facility operation modeling and simulation based primarily on a discrete event system modeling scheme. Many modern industrial facilities are so complex that their operational status cannot be estimated by simple calculations. In general, a facility can consist of many processes and transfers of material between processes that may be modeled as a discrete event system. This paper introduces the current status of studies on operation modeling and simulation for typical nuclear facilities, along with some examples. In addition, this paper provides insights about how a discrete event system can be applied to a model for a nuclear facility. A headend facility is chosen for operation modeling and the simulation, and detailed procedure is thoroughly described from modeling to an analysis of discrete event results. These kinds of modeling and simulation are very important because they can contribute to facility design and operation in terms of prediction of system behavior, quantification of facility capacity, bottleneck identification and efficient operation scheduling.

• Journal of Computational Design and Engineering
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• 제1권4호
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• pp.233-242
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• 2014

A magnetically levitated vehicle (Maglev) system is under commercialization as a new transportation system in Korea. The Maglev is operated by an unmanned automatic control system. Therefore, the plan of train operation should be carefully established and validated in advance. In general, when making a train operation plan, statistically predicted traffic data is used. However, a traffic wave often occurs in real train service, and demand-driven simulation technology is required to review a train operation plan and service quality considering traffic waves. We propose a method and model to simulate Maglev operation considering continuous demand changes. For this purpose, we employed a discrete event model that is suitable for modeling the behavior of railway passenger transportation. We modeled the system hierarchically using discrete event system specification (DEVS) formalism. In addition, through implementation and an experiment using the DEVSim++ simulation environment, we tested the feasibility of the proposed model. Our experimental results also verified that our demand-driven simulation technology can be used for a priori review of train operation plans and strategies.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.556-559
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• 2007

The notion of linearity is fundamental in science and engineering. Much of system and control theory is based on the analysis of linear system, which does not care whether it is nonlinear and complex. The dynamic programming is one of concerned technology when users are interested in choosing best choice from system operation for nonlinear or dynamic system‘s performance and control problem. In this paper, we will introduce the dynamic programming which is based on discrete system. When the discrete system is constructed with discrete state, transfer between states, and the event to induct transfer, the discrete system can describe the system operation as dynamic situation or symbolically at the logical point of view. We will introduce technologies which are related with controllable of Controlled Markov Chain as shown example of simple game. The dynamic programming will be able to apply to optimal control part which has adaptable performance in the discrete system.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.400-408
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• 2009

Simulation applications for analyzing the productivity of construction operations at operation level and project schedules at project level are crucial methods in project management. The application at two different levels should be very tightly linked to each other in practice. However, appropriate integration at the levels is not achieved in that existing systems do not support to integrate operation models into a schedule model. This paper presents a new approach named to Discrete Event Simulation-Nesting modeling approach, which supports not only productivity analysis at operation level but also schedule management at a project level. The system developed by the authors allows creating operation models at the operation level, maintaining them in operation model library, executing sensitivity analysis to find the behaviors of the operation models when different combination of resources are used as existing DES systems do. On top of the conventional functions, the new system facilitates to find the optimum solution of resource combinations which satisfy the user's interest by computing the hourly productivity and the hourly cost of the operation. By drag-and-dropping an operation model kept in the operation model library, the operation models are integrated into an activity of the schedule model. When a complete schedule model is established by nesting operation models into the schedule model, stochastic simulation based scheduling is executed. A case study is presented to demonstrate the new simulation system and verify the validity of the system.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.196-197
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• 2014

Low carbon construction is an important operation management goal such as cost, time, and quality in construction community. This paper introduces a system which measures the variability of carbon dioxide amounts. First, this system allows creating construction operation models of which the level of detail is breakdown into the work task level. Second, the system implements sensitivity analysis along with a ranges of resources that are allocated in an operation model. It facilitates to find the optimal resource combination using the operation performances such as the amount of emissions, operation completion time, and cost. Lastly, it identifies the best fit probability distribution functions of performance criteria given a certain resource combination. It allows project manager to query the percentages to complete the operation within a limitation specified by the system users.

• 산업경영시스템학회지
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• 제31권2호
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• pp.19-27
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• 2008

This paper addresses determining the location of the distribution centers in a discrete dynamic distribution system. In discrete and finite time horizon, the demands of retailers are dynamic for the periods. Some locations among the retailers can be chosen for the role of the distribution centers at the beginning of each period. The distribution centers have to be located at the location of minimizing logistics cost. Logistics cost factors are the operation cost and the fixed cost of distribution center, and the transportation cost. The distribution centers of minimizing sum of operation cost, fixed cost and transportation cost are determined among retailers in each period for the planning period. A mathematical model was formulated and a dynamic programming based algorithm was developed. A numerical example was shown to explain our problem.

• 한국해안해양공학회지
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• 제5권2호
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• pp.133-142
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• 1993

컴퓨터로 제어하는 조파시스템을 보다 정교하게 제어하기 위해서는 제어회로 구성에 있어서 조파판의 이산적 전달작용을 반영할 필요가 종종 있다. 본 연구에서는 시간영역에서 조파판의 전달 작용을 이산적으로 모의할 수 있는 수치필터를 설계하였다. 필터의 효능성을 파악하기 위하여 규칙 또는 불규칙 조파판 입력데이타를 가지고 예제 해석을 시도하였다. 필터의 출력을 이론적 정확치 또는 이산회적 출력과 비교한 결과, 이들이 매우 잘 일치함을 확인하였다. 이용된 필터 구현방법은 사실상 이중선형변환 방법이며, 이 방법에는 주파수 착각 오차가 배제되기 때문에 주파수대가 한정되어 있지 않은 조파판 전달함수에 대해서도 충분히 정확성을 갖고 통용될 수 있음을 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.439-443
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• 1987

This paper presents a method for constructing model of manufacturing processes for simulation and design of the discrete control logic. The models represent the discrete vent evolution of the system as well as features of the underlying continues processes, for applications such as discrete parts manufacture and assembly, the process is decomposed into operations and for each operation the required resources and associated discrete resource slates are Identified. The structure of the discrete-level control is modeled by modified Perti nets which are synthesized from single resource activity cycles. Construction of nets provides discrete control logic with guaranteed properties based on extended Petri nets theory, for illustration, the proposed method is applied to the high-level discrete control of a two-robotic assembly cell.

• 한국시뮬레이션학회논문지
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• 제20권3호
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• pp.89-100
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• 2011

새로운 교통수단으로서 실용화가 진행 중인 자기부상열차 시스템은 무인자동운전으로 운영되며, 사전에 면밀한 열차운행 계획의 수립과 검증이 요구된다. 일반적으로 열차운행 계획을 수립할 때는, 노선계획에 따른 통계화된 수송수요 예측자료를 활용하지만, 실제 열차 운행 시에는 수송 파동이 생길 수 있으며, 이를 고려하여 열차 운행 계획과 서비스 품질을 사전에 검토할 수 있는 수요기반 시뮬레이션 기술이 요구된다. 본 연구에서는 연속적인 수요파동을 반영할 수 있는 자기부상열차 운행 시뮬레이션 방법 및 모델을 제시하였다. 이를 위해, 열차 운행에 따른 승객 수송과정을 가장 효과적으로 모사할 수 있는 이산사건 모델을 적용하였으며, DEVS 형식론을 이용하여 시스템을 체계적으로 모델링 하였다. 또한, DEVSim++시뮬레이션 환경을 이용한 구현과 실험을 통해, 제안한 모델에 대한 구현 가능성을 검증하였고, 이러한 수요기반 시뮬레이션을 이용하면 운행계획과 전략에 대한 효과적인 사전 검토가 가능함을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.262-271
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• 2017

This paper presents a novel concept of phase swapping to associate multiple flux weakening ranges to a non-salient PM machine without altering any hardware of the machine. The proposed concept enables a dual three-phase machine to be operated with different displacement angles between the two three-phase windings. Hence, different flux weakening ranges using winding switching can be accomplished by applying this concept. It was also demonstrated that the proposed concept can be utilized for the discrete step as well as continuous operation of the machines. Any application requiring a wide speed range operation of up to thirteen times the base speed can benefit from this proposed concept. Analytical, simulation, and experimental results are provided to validate the effectiveness of the proposed concept.